Observation of Arc Trails with Significant Damage due to Glow Discharge Wall Conditioning in the Large Helical Device

Abstract

We report the observation of arcing damage on the diagnostic shutter during the glow discharge wall conditioning in LHD. The diagnostic system has no experience of plasma discharge produced by electron or ion cyclotron resonance heating or neutral beam injection. The arc trails were observed on the aluminum surface but not on the stainless steel although both materials were exposed to the glow discharge with the same duration. The difference in work functions between two materials may be a cause to divide the conditions of arcing ignition.